build(deps): bump com.google.cloud:google-cloud-spanner-hibernate-tools (GoogleCloudPlatform#3324)

Bumps [com.google.cloud:google-cloud-spanner-hibernate-tools](https://github.com/GoogleCloudPlatform/google-cloud-spanner-hibernate) from 3.9.3 to 3.9.4.
- [Release notes](https://github.com/GoogleCloudPlatform/google-cloud-spanner-hibernate/releases)
- [Changelog](https://github.com/GoogleCloudPlatform/google-cloud-spanner-hibernate/blob/master/CHANGELOG.md)
- [Commits](GoogleCloudPlatform/google-cloud-spanner-hibernate@v3.9.3...v3.9.4)

---
updated-dependencies:
- dependency-name: com.google.cloud:google-cloud-spanner-hibernate-tools
  dependency-version: 3.9.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]